From a06abadc822767d43bfb1885dcc7df257f4dce51 Mon Sep 17 00:00:00 2001
From: Ziggy Jonsson <ziggy.jonsson.nyc@gmail.com>
Date: Sun, 19 May 2019 09:51:03 -0400
Subject: [PATCH] Add crx to Open Buffer

---
 README.md          |  2 ++
 lib/Open/index.js  | 18 ++++++++++++++++--
 test/openBuffer.js | 10 ++++++++++
 3 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index 7d75d38..e350f6b 100644
--- a/README.md
+++ b/README.md
@@ -27,6 +27,8 @@ There are no added compiled dependencies - inflation is handled by node.js's bui
 
 Please note:  Methods that use the Central Directory instead of parsing entire file can be found under [`Open`](#open)
 
+Chrome extension files (.crx) are zipfiles with an [extra header](http://www.adambarth.com/experimental/crx/docs/crx.html) at the start of the file.  Unzipper will parse .crx file with the streaming methods (`Parse` and `ParseOne`) and `Open.buffer` method.
+
 ## Installation
 
 ```bash
diff --git a/lib/Open/index.js b/lib/Open/index.js
index a6148f4..0756b8d 100644
--- a/lib/Open/index.js
+++ b/lib/Open/index.js
@@ -2,13 +2,28 @@ var fs = require('fs');
 var Promise = require('bluebird');
 var directory = require('./directory');
 var Stream = require('stream');
+var binary = require('binary');
 
 // Backwards compatibility for node versions < 8
 if (!Stream.Writable || !Stream.Writable.prototype.destroy)
   Stream = require('readable-stream');
 
 module.exports = {
-  buffer: function(buffer) {
+  buffer: function(buffer) {  
+    // slice the buffer to correct start location if crx files
+    var signature = buffer.readUInt32LE(0);
+    if (signature === 0x34327243) {
+      var baseHeaderLength = 4*4;
+      var h = binary.parse(buffer)
+        .word32lu('signature')
+        .word32lu('version')
+        .word32lu('pubKeyLength')
+        .word32lu('signatureLength')
+        .vars;
+
+      buffer = buffer.slice(baseHeaderLength +  h.pubKeyLength + h.signatureLength);
+    }
+
     var source = {
       stream: function(offset, length) {
         var stream = Stream.PassThrough();
@@ -92,4 +107,3 @@ module.exports = {
     return directory(source);
   }
 };
-
diff --git a/test/openBuffer.js b/test/openBuffer.js
index 8ca4f46..ed09a6b 100644
--- a/test/openBuffer.js
+++ b/test/openBuffer.js
@@ -22,4 +22,14 @@ test("get content of a single file entry out of a buffer", function (t) {
           t.end();
         });
     });
+});
+
+test('open buffer containing a crx file', function(t) {
+  var archive = path.join(__dirname, '../testData/compressed-standard-crx/archive.crx');
+  var buffer = fs.readFileSync(archive);
+  return unzip.Open.buffer(buffer)
+    .then(function(d) {
+      t.same(d.files[1].path, 'dir/fileInsideDir.txt');
+      t.end();
+    });
 });
\ No newline at end of file